Method of forming thermocouples



April 1941 H. T. SPARROW ET AL 2,278,744

METHOD OF FORMING THERMO-COUPLES Filed May 15, 1940 inventor Hubert T.Sparrow- J 614.14. M. Wi l s on.-

attorney,

Patented Apr. 7, 1942 METHOD OF FORWNG THERMOCOUPLES I Hubert T. Sparrowand John M. Wilson, Minneapolis, Minn, assignors toMinneapolis-Honeywell Regulator Company, Minneapolis, Minn, acorporation of Delaware Application May 13, 1940, Serial No. 334,812

9 Claims.

The present invention is concerned with a new and novel thermo-coupleunit and particularly with a novel method of making the same.

A thermo-couple is composed of a pair of metals having dissimilarthermo-electric characteristics, which metals are permanently joined atone end to form a hot junction and are adapted to be electrically joinedat the other end to form a cold junction. Where a plurality ofthermo-couples are employed, the device is known as a thermopile.Thermo-couples are usually relatively expensive to construct and this isparticularly true in the case of thermopiles. The present invention hasas its object the provision of a thermo-couple which can be formed witha relatively simple process and is particularly concerned with theprocess of making the same.

The present invention accomplishes this object by providing athermo-couple in the form of a flat member which can be formed by aplurality of cutting operations. These cutting operations may if desiredbe accomplished by stamping. The various units are formed from a longstrip composed of a plurality of component strips of dissimilar metalssecured together along their longitudinal edges, this strip being cuttransversely at spaced points to provide a plurality of relatively shortsections. The material along the joints between the component strips ofeach sec- 111 tion is then cut away for the greater portion of thelength of the strips to provide series connected thermo-couple members.The resulting unit may then be rolled, if desired, to provide a morecompact arrangement.

For a more complete understanding of the invention, reference is made tothe accompanying specification, claims and drawing of which:

Figure l is a perspective view of the strip from which the individualsections are cut;

Figure 2 is a view of one individual section of the strip with dottedlines to indicate where the material is cut away;

Figure 3 is a perspective view of one form of the completedthermo-couple device; and

Figures 4 and 5 are perspective views of modified forms of our device.

The first step in the novel process of the present invention is to forma strip comprising a plurality of pairs of metallic strips, each paircomprising two strips of dissimilar thermo-electric characteristics,said strips all being joined along their longitudinal edges. Aspreviously indicated, this strip is shown in Figure 1. Referring to thisfigure, the strip itself is designated one desirable method is to rollthese members together while hot so as to weld them together in therolling process. If the members are formed by such a rolling process, itis possible to have the strip Ill in the form of a continuous strip.

At uniformly spaced points designated by the dotted lines l8 and IS, thestrip I0 is cut transversely to the length thereof to provide aplurality of short sections. One of these sections I is shown in Figure2 and is designated by the reference character 20.

The last step in the formation of one form of the thermopile is toremove material adjacent the joints to electrically separate thecomponent strips for the greater portion of their length. The dottedlines 22 and 23 enclose the areas cut away along the joints betweenstrips l2 and i3 and between strips [4 and I5. It will be noted that bycutting away this portion two slots are provided separating the stripsl2 and 13 on the one hand and strips M and IS on the other hand for thegreater portion of the length of these strips. A dotted line 24 enclosesthe portion which is cut out adjacent one end of the section and whichis cut out between strips II and l2, l3 and M, and i5 and I6. It will benoted that between strips H and l2, l3 and I4, and i5 and IS the dottedlines extend within a short distance of the far end of section 20. Thedotted line 24 further encloses a rectangular piece extending from thenear end of its strip to the portion 28 of dotted line 24. It will benoted that this rectangular portion includes the near ends of strips l2,l3, I4 and I5 leaving a portion of strips II and I6 projecting outwardlyfrom the remaining portion of section 20. The dotted lines 29 and 30enclose circular portions to provide apertures through the projectingends of strips II and IS.

The particular manner in which the portions outlined in dotted lines areremoved forms no part of the present invention although it is to beunderstood that such material can be removed by a single die stampingoperation, using dies of relatively simple form.

In Figure 3 one form of the completed product is shown. The slots formedby cutting away the portion enclosed by dotted lines 22 and 23 aredesignated in this figure by reference numerals 32 and 33. The slotsbetween members I l and l2, l3 and I4, and I5 and it are designated bythe reference numerals 35, 86 and 81, respectively. It will be notedthat alternate slots extend from opposite ends of the section. Theresult is that strips H to IE are connected together in series by theremaining uncut portions of the joints between these strips. It isusually desirable, where a plurality of thermo-couples are employed, toconnect them in series as is done by extending alternate slots inalternate directions in the manner shown. It is also possible to connectthe constituent thermo-couples in parallel by extending the slots in thesame direction and providing suitable jumpers to connect the variouselements together.

The projecting ends of strips II and [6 are designated in Figure 3 bythe reference characters 40 and 4 I the apertures therethrough formed bythe removal of the material within dotted lines 29 and 30 beingdesignated by the reference numerals 42 and 44. It will be noted thatthe projecting ends 40 and 4| have been bent upwardly. These ends aredesigned to form terminalportions for the'thermopile unit and may ifdesired also be employed for maintaining the unit. The apertures 42 and44 may be tapped so as to provide for the receptionof screws therein.

The device of Figure 4 is similar to Figure 3 with the exception thatafter the portions between the component strips are cut away, the stripis subjected to a rolling operation. It will be noted that in thisspecies, the terminals 50 and 5| corresponding to terminals 40 and ll ofFigure 3 are not bent transversely to the strip but merely extendlongitudinally therefrom. The

-form of Figure 4 is desirable where the burner is of the conventionaltype with a flame of substantially circular cross-section.

In Figure 5 there is shown a still further modiflcation of our device.In this form of the device, there are a relatively large number ofcomponent strips so as to provide a large number of thermocouple units.The strip itself is of considerably greater width than in the species ofFigures 1 to 4 and is preferably of somewhat thinner material. After thestrip is subjected to the stamping operation indicated in dotted linesin Figure 2, the strip has a layer of insulating material disposedadjacent it and is rolled spirally to form the compact unit shown inFigure 5. In this figure, the insulating layer is designated by thereference numeral 54. It will be noted that in the form shown, there aretwelve thermocouples and in spite of this, the space occupied is notparticularly greater than that occupied by the species of Figure 4. Thedevice does have the disadvantage however over that of Figures 3 and 4in that a somewhat greater time is required for cooling of thehotjunction of the thermocouples due to the fact that they are closertogether and hence radiate the heat more slowly. Where the time ofresponse is not of theutmost importance however, the arrangement ofFigure 5 is desirable by reason of its relative compactness.

It will be seen that by reason of the present invention, it'is possibleto manufacture thermocouples or thermopiles by an extremely simpleprocess. While we have shown a specific embodiment of our invention, itis to be understood that the scope thereof the appended claims.

We claim as our invention:

1. The method of forming thermo-electric devices which comprises thesteps of assembling a. plurality of strip members in side by siderelation and in which the strips adjoining any one strip havethermo-electric characteristics dis-- similar from the thermo-electriccharacteristics of said one strip, heating and rolling the said stripmembers to join them along their longitudinal. side edges to theadjacent strip members to form a sheet of material, cutting said sheettrans versely to provide a plurality of relatively short sections,separating adjacent strips for the greater portion of the length of eachsection by removing material from along each joint, the separation ofthe strips along adjacent joints extending from opposite ends of thesection and the resulting structure being a continuous strip in whichmembers having dissimilar thermoelectric characteristics are joined inseries with alternate joints at one end of said sheet of material.

2. The method of manufacture of'a thermocouple device comprising thesteps of forming a strip of material composed of a plurality ofmonometal strip members joined in edgewise relation, the alternate stripmembers having predetermined thermo-electric characteristics andadjacent strip members having dissimilar thermoelectric characteristics,heating the said strip members and joining them while so heated in saidside by side relation to form said strip of material, separating thestrip members along and for the greater portion of the length of eachjoint by removing material from along each joint, the said separationalong adjacent joints extending to opposite ends of said strip ofmaterial to form the strip members into a continuous series in which amember is connected to members having dissimilar thermo-electriccharacteristics with alternate joints located at one end of said stripof material.

3. The method of manufacture of a thermocouple device comprising thesteps of forming a is to be limited only by strip ofmaterial composed'ofa plurality of monometal strip members joined in edgewise relation, thealternate strip members having predetermined thermo-electriccharacteristics and adjacent strip members having dissimilarthermoelectric characteristics, heating the said strip members andjoining them while so heated in said side by side relation to form saidstrip of material, separating the strip members along and for thegreater portion of the length -of each 4. The method of manufacture of athermocouple device comprising the steps of forming a strip of materialcomposed of a plurality of monomined thermo-electric characteristics andadjacent strip members having dissimilar thermoelectric characteristics,heating the said strip members and joining them while so heated in saidside by side relation to form said strip of material, separating thestrip members along and for the greater portion of the length of eachjoint by removing material from along each joint. the said separationalong adjacent joints extending to opposite ends of said strip ofmaterial to form the strip members into a continuous series in which amember is connected to members having dissimilar thermo-electriccharacteristics with alternate joints located at one end of said stripof material, and bending said strip of material about an axislongitudinal of the said strips.

5. The method of manufacturing a composite metal strip employed in themanufacture of thermo-electric devices comprising, the steps ofassembling in side by side relation a plurality of mono-metal stripmembers and in which the members adjacent to any one ofthe members havethermo-electric characteristics dissimilar to those of said one memberand with alternate members having similar thermo-electriccharacteristics, heating the said plurality of strip members, androlling the said members while hot to weld the strips together along thelongitudinal side edges of adjacent strips to form a composite metalstrip for use in the manufacture of thermoelectric devices.

6. The method of manufacturing thermo-electric devices from a compositemetal strip comprising a plurality of mono-metal strip members joinedalong their longitudinal side edges, the

7 adjacent members of said strip having dissimilar thermo-electriccharacteristics and alternate members having similar thermo-electriccharacteristics, the steps comprising separating said members for thegreater portion of the length of each joint by removing metal from alongeach joint, the metal removed from one joint extending to one end ofsaid strip and the metal removed from the adjacent joints extending tothe opposite end of said strip to thus form a single continuous strip inwhich the component strip members are connected in series with alternateconnecting joints extending to one edge of said strip.

'7. The method of manufacturing thermo-electric devices from a compositemetal strip comprising a plurality of mono-metal strip members joinedalong their longitudinal side edges, the adjacent members of said striphaving dissimilar thermo-electric characteristics and alternate membershaving similar thermo-electric characteristics, the steps comprisingseparating said members for the greater portion of the length of eachjoint by removing metal from along each joint, the metal removed fromone joint extend ing to one end of said strip and the metal removed fromthe adjacent joints extending to the opposite end of said strip to thusform a single continuous strip in which the component strip members areconnected in series with alternate connecting joints extending to oneedge of said strip and removing material from between the separatedendsrof the outermost strips to provide electrical terminals for saidthermo-couple device consisting of the extended and separated ends ofsaid outermost strips.

8. The method of manufacturing thermo-electric devices from a compositemetal strip comprising a plurality of mono-metal strip members joinedalong their longitudinal side edges, the adjacent members of saidwstriphaving dissimilar thermo-electric characteristics and alternate membershaving similar thermo-electric characteristics, the steps comprisingseparating said members for the greater portion of the length of eachjoint by removing metal from along each joint, the metal removed fromone joint extending to one end of said strip and the metal removed fromthe adjacent joints extending to the opposite end of said strip to thusform a single continuous strip in which the component strip members areconnected in series with alternate connecting joints extending to oneedge of said strip and bending said strip of material about an axislongitudinal of the said strips.

9. The method of manufacturing thermo-electrio devices from a compositemetal strip comprising a plurality of mono-metal strip members joinedalong their longitudinal side edges, the adjacent members of said striphaving dissimilar thermo-electric characteristics and alternate membershaving similar thermo-electric characteristics, the steps comprisingseparating said members for the greater portion of the length of eachjoint, the separation of one. joint extending to one end of said stripand the separation of the adjacent joints extending to the opposite endof said strip to thus form a single continuous strip in which thecomponent strip members are connected in series with alternateconnecting joints extending to one edge of said strip, bending the saidstrip of material about an axis longitudinal of the said strips to forma roll; and adding insulating material between adjacent layers of thethus formed roll.

HU'BERT T. SPARROW.

JOHN M. WILSON.

